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position measurement

In industrial distance and position measurement applications, one size definitely does not fit all. Depending on the application, the position or distance to be measured can range from just a few millimeters up to dozens of meters. No single industrial sensor technology is capable of meeting these diverse requirements.

Fortunately, machine builders, OEM’s and end-users can now choose from a wide variety of IO-Link distance and position measurement sensors to suit nearly any requirement. In this article, we’ll do a quick rundown of some of the more popular IO-Link measurement sensor types.

These sensors, available in tubular and block style form factors are used to measure very short distances, typically in the 1…5 mm range. The operating principle is similar to a standard on/off inductive proximity sensor. However, instead of discrete on/off operation, the distance from the face of the sensor to a steel target is expressed as a continuously variable value. Their extremely small size makes them ideal for applications in confined spaces.

Inductive Linear Position Sensors

Inductive linear position sensors are available in several block style form factors, and are used for position measurement over stroke lengths up to about 135 mm. These types of sensors use an array of inductive coils to accurately measure the position of a metal target. Compact form factors and low stroke-to-overall length factor make them well suited for application with limited space.

Magnetostrictive Linear Position Sensors

IO-Link Magnetostrictive linear position sensors are available in rod style form factors for hydraulic cylinder position feedback, and in external mount profile form factors for general factory automation position monitoring applications. These sensors use time-proven, non-contact magnetostrictive technology to provide accurate, absolute position feedback over stroke lengths up to 4.8 meters.

Laser Optical Distance Sensors

Laser distance sensors use either a time-of-flight measuring principle (for long range) or triangulation measuring principle (for shorter range) to precisely measure sensor to target distance from up to 6 meters away. Laser distance sensors are especially useful in applications where the sensor must be located away from the target to be measured.

The proliferation of available IO-Link measurement sensors is made possible, in large part, due to the implementation of IO-Link specification 1.1, which allows faster data transmission and parameter server functionality. The higher data transfer speed is especially important for measurement sensors because continuous distance or position values require much more data compared to discrete on/off data. The server parameter function allows device settings to be stored in the sensor and backed up in the IO-Link master. That means that a sensor can be replaced, and all relevant settings can be downloaded from master to sensor automatically.

To learn about IO-Link in general and IO-Link measurement sensors in particular, visit www.balluff.com.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.

Hydraulic actuators can be used to open and close a valve’s position. In automation architectures, a linear position sensor is used within the hydraulic actuator to provide continuous position feedback.

The linear position sensor is installed into the back end of the cylinder. The sensing element resides in a cavity that has been gun-drilled through the piston and cylinder rod, extending the full length of the mechanical stroke. A magnet ring is used as a position marker and mounted on the face of the piston. As the piston (and the position marker) move, the linear position sensor provides a continuous absolute position by way of an analog or digital signal.

In some applications, a cylinder’s position may only be moving across a small portion of the overall stroke or a specific portion of the stroke. The end user could benefit from altering the transducer’s signal based on the application’s specific stroke requirements instead of the entire cylinder’s stroke, thereby maximizing available position resolution. When this situation arises, most transducer manufacturers offer the ability to customize or “teach” a modified output of the stroke via push buttons or from wiring inputs. When this is done, the process does require the cylinder (and position marker) to move to these defined locations for a “teach”.

A more user-friendly and repeatable approach for customized stroke lengths with linear position sensors is to use a graphical software package. The software can be connected
from a PC via USB to a compatible linear position sensor. Starting and ending stroke values can be precisely entered into the software and a graphical representation of the output curve is created. For a more straightforward approach, you can also drag and drop these stroke points by a click of a cursor. The file can be saved on a PC and downloaded to the transducer. In either case, the cylinder’s piston doesn’t need to be actuated.

In projects where multiple, identical actuators and linear position sensors need to be customized, the setup would only need to be done once, the file saved, and simply uploaded to all the sensors for the project. A great time-saver over manually teaching each and every sensor.

Another benefit to using software with linear position sensors is to be able to upload programs for replacement units in a safe user environment (e.g. lab station or office) and shipping them to various job sites. These different locations (or locales) can be in harsh environmental conditions (extreme cold or heat) or areas that contain ignitable or explosive gases or dusts which may be difficult to work in.

Other software features include inverting the output curves, offering position or velocity outputs, and more.

For more information on Balluff’s Magnetostrictive Linear Position Sensors, visit www.balluff.com.

In addition to distribution, we design and fabricate complete engineered systems, including hydraulic power units, electrical control panels, pneumatic panels & aluminum framing. Our advanced components and system solutions are found in a wide variety of industrial applications such as wind energy, solar energy, process control and more.